This invention relates to incinerators and furnaces and, more particularly, to systems for removing ash and residue from a furnace while maintaining and controlling the flow of combustion air.
Disposal of municipal and industrial refuse is a critical problem due to a shortage of landfill sites. Burning such refuse is a desirable alternative because it greatly reduces the volume of waste. Burning has an added benefit because incinerators using refuse as fuel can also be used to generate usable energy.
However, due to the heterogeneous nature of such refuse, it is difficult to maintain a degree of efficiency in the combustion process. Efficient combustion in an incinerator may be facilitated by controlling the pressure and volume of combustion air within the combustion chamber. Unfortunately, the process of disposing of residue and ash from the furnace can disturb the balance of pressure and temperature within the combustion chamber. As a result, it is often a problem for incinerator ash removal systems to dispose of ash while maintaining the combustion chamber air seal. This problem is even more acute in furnaces requiring precise control over combustion chamber temperature and pressure.
For example, in incinerators using municipal and industrial refuse as fuel, it may be desired to have independent control of the combustion environment within various sections of the incinerator. This is because such refuse varies widely in bulk, density, moisture and combustibility. This variation in the combustibility of the refuse makes it difficult to burn the refuse in an efficient manner due to the inability to maintain a fuel bed of uniform density.
One approach to this problem is to provide a large supply of combustion air for fast burning components of the refuse, and to provide a reduced combustion air flow to the slower burning refuse components. One example of an incinerator of this type is U.S. Pat. No. 3,126,846. That patent employs a movable grate to convey burning refuse along the grate surface. Multiple sections of the grate are supplied with a source of combustion air that varies in pressure and volume for each section depending on the rate of desired burning in that section. In incinerators with movable grates, however, some of the ash or residue will inevitably fall through the grate in the form of siftings. A problem arises in removing the siftings in an automatic and efficient manner, without disturbing the control of the airflow into the various portions of the combustion chamber.
Thus, it is an object of the present invention to provide a method for automatically removing ash siftings falling through a furnace grate.
Another object of the present invention is to provide a system for removing siftings from a grate that does not disturb the controlled air flow to separate sections of a grate.
A further object of the present invention is to provide all of the above objects in a system that is cost efficient and minimizes the number of components that must be added to the incinerator.